A Bioclimatic Design Approach to the Energy Efficiency of Farm Wineries: Formulation and Application in a Study Area

Abstract

Wineries require a significant energy demand for cooling interior spaces. As a result, designing energy-efficient winery buildings has become a crucial concern for winemaking countries. The objective of this study was to evaluate six winery building models with bioclimatic designs, located in the Guadalupe Valley, Baja California, using data on thermal performances (indoor temperature and relative humidity) and energy consumption obtained through dynamic thermal simulation. A baseline winery building model was developed and then enhanced with bioclimatic strategies: a semi-buried building; an underground cellar; an underground cellar with the variants of a green roof, double roof, shaded walls, and polyurethane insulation. The last solution entailed the requirement of a reduction in cooling in the warm season by 98 MWh, followed by the one with a green roof, corresponding to 94 MWh. This study provides valuable insights into the effectiveness of different architectural approaches, offering guidelines for the design of functional buildings for wine production, besides presenting energy-efficient solutions for wineries tailored to the climatic conditions of the study region. These findings highlight the importance of a function-based and energy-efficient architectural design in the winemaking industry, which leads to the definition of buildings with a compact arrangement of the functional spaces and a fruitful integration of the landscape through a wise adoption of underground solutions.

1. Introduction

Winery buildings should provide adequate spaces for wine production, aging, and conservation, with a strict control of environmental conditions. This kind of requirement calls for energy-efficient constructions with a controlled thermal performance [1]. For this reason, optimal design criteria are closely dependent on the climatic conditions of the construction site, which has to be suitable for grapevine cultivation [2].

A wine cellar can be defined as a building devoted to wine production, preservation, and storage, with possible additional spaces for direct selling and wine tasting. It is a structure that requires specific and controlled indoor environmental conditions to ensure the quality of the final product [3]. The scientific literature highlights the importance of the assessment and control of cooling and refrigeration loads in wineries [4] in order to support technicians in developing accurate profiles of energy demand. In wine cellars, the required levels of dry bulb temperature (DBT) and relative humidity for wine production and aging processes, as well as the diversity of materials and construction systems used, make it necessary to employ active cooling, heating, or humidification systems in interior spaces. This leads to increased energy consumption and impacts the economic cost of environmental conditioning within the building operations at the expense of wine-producing farms. Energy use for wine production has been analyzed in the scientific literature within the framework of fostering energy efficiency and also in specific brand production [5,6]. In this regard, a recent study [7] developed a methodology to foster energy efficiency in wine production, and it demonstrated its effectiveness in enabling accurate benchmarking of energy performance in wineries.

The interior ambient temperature range required for spaces designated for wine aging is between 10 °C and 15 °C; for the production area, it ranges from 15 °C to 25 °C [8]. Regarding relative humidity, the minimum limit reported in various studies is 30%, and the maximum is 75% [9]. Other authors have defined the acceptable range for relative humidity within wine cellars to be between 60% and 80%, arguing that excessive humidity can lead to the growth of undesirable microorganisms, whereas levels below this range can dry corks, causing osmotic pressure to draw wine into the cork [10]. The control of relative humidity is essential in the wine aging area to prevent condensation and reduce wine loss due to evaporation inside the barrels, which can range from 1% to 9% of the total stored production. Temperature changes outside the above range (from 10 °C to 15 °C for wine aging), on the other hand, can delay or accelerate the phenological processes of grape must and alter its taste and quality. Therefore, the need for interior environmental control, which is critical in cases of an inadequate design of wine cellars with respect to the local climate, directly affects artisanal small-scale wine producers because of their limited financial capacity to cover electricity consumption costs. This also leads to an increase in energy consumption—with consequent probable GHG emissions—and in the final production costs, thus reducing their competitiveness in local, national, and international markets. At the same time, the goal of energy efficiency and the need for an effective control of environmental parameters in wine cellars call for specific and innovative construction solutions, sometimes drawing inspiration from traditional local building technologies [11]. The sustainability of wine production has been analyzed in the scientific literature for several years, with reference to European wines [12] and the extra-EU winemaking sector [13].

These issues are observed in a prominent region known for its favorable conditions for wine production—the Guadalupe Valley in Baja California, Mexico—where a Mediterranean-type microclimate (Csa) is recorded [10], which is ideal for the cultivation of grape varieties. In fact, it is the largest and most important wine-producing area in Mexico due to its production volume and optimal geographic location for vine cultivation, which is between 30° and 50° latitudes north, which allow it to compete with wines from France, Spain, and Italy. This is why 90% of Mexican wine (which was 38,000 m³ in 2023 [14]) is produced in this region, and it is the wine tourism area with the greatest economic affluence in the country [15].

Despite the microclimatic requirements, the architectonic features and construction materials used for winery buildings located in a given area, like the abovementioned one, are often diverse, as the form may have greater weight than the function, due to several reasons linked to the local building culture, architectural traditions, or specific advantages, such as the attractiveness for tourism of the building design. The latter criterion could leave aside or even omit the construction characteristics necessary to achieve an interior thermal environment suitable for wine processing and aging. With reference to the Guadalupe Valley, some small producers in the region have implemented passive adaptation strategies in their buildings, in certain cases empirically, to reduce costs for electricity consumption for the production, aging, and storage of wine. However, the optimal ambient temperature and indoor relative humidity requirements for wine production, predominantly during the warmer period of the year, make it necessary to use electromechanically active systems for cooling and humidification most of the day, which increases energy consumption.

The variability in the typologies of wine cellars constructed in the Guadalupe Valley became clear upon carrying out observational analyses through preliminary surveys of the area. In the valley, wine cellars show different configurations of story levels, as they are built at the ground level, semi-buried, fully buried, underground, or in combined configurations. The construction materials are diverse, and artisanal wine cellars are generally self-constructed, following architectural principles rooted in empirical rules. This contributes to the Guadalupe Valley’s distinctive and eclectic wine architecture within the rural context (Figure 1). This situation has partly arisen due to the absence of current legislation at the national, state, or municipal levels that regulates the construction of such facilities, contrasting with the legal frameworks governing wine cellars in European countries.

The diversity of materials and construction systems, as well as the wine production and storage processes in cellars, calls for the use of active cooling, heating, or humidification systems in interior spaces. This results in increased energy consumption and higher costs for indoor environmental conditioning. Such a situation directly impacts artisanal producers, who have less financial capacity (compared to industrial producers) to bear the costs associated with electricity usage in their cellars. Consequently, this leads to higher final product prices and reduces their competitiveness in the market. Furthermore, the wine cellars constructed in the Guadalupe Valley are primarily designed to address social and tourism needs, often giving less consideration to climatic factors. This is linked to the region’s economic capacity and the impact of the viticultural industry in the state, which has promoted rapid tourism growth in the last decades and, at the same time, accelerated the establishment of new wineries.

From the above, it can be deduced that buildings intended for wine production in the Guadalupe Valley must consider the climate as a determinant of form, construction materials, and orientation. Active or passive design strategies should be implemented to achieve suitable interior thermal conditions, as neglecting these factors can increase energy consumption and impact profitability. In warm climates, 34% of energy use is indeed attributed to cooling spaces and mitigating heat gain from solar radiation [16], an issue that can be addressed through the bioclimatic design of the building envelope.

A bioclimatic assessment of a specific city or region helps define passive strategies that, when applied to buildings, can achieve acceptable thermal conditions or thermal comfort for specific users under defined circumstances. In this case study, the assessment focuses on the typologies of wine production—primarily white and red wines artisanally made—and the functional areas of the building identified as key for winemaking and winery operations.

Various studies on the thermal monitoring of wine cellars have primarily been conducted in Spain and Italy. Mazarrón and Cañas [17] analyzed the thermal behavior of three traditional underground wine cellars in the Ribera del Duero region of Spain, characterized by a continental Mediterranean climate. They concluded that interior temperature has a 96% correlation with external temperature, while the subsurface temperature mitigates fluctuations that could compromise wine preservation. The significance and extended duration of the wine aging process have led to several studies focused on the hygrothermal conditions of aging rooms [18]. Many of these investigations examined the performance and/or effectiveness of specific construction designs [19]. For instance, Barbaresi et al. [20] evaluated the effectiveness of various retrofit interventions to improve thermal performance in unconditioned above-ground farm buildings, while Torreggiani et al. [21] studied the role of architectural elements in enhancing the thermal behavior of similar structures. Barbaresi et al. [22] developed a method to ensure reliability in energy simulations for modeling underground cellars, providing a dependable tool for energy-efficient building and system design, while Mazarrón et al. [3] further investigated the feasibility of using agro-industrial building basements for wine aging and preservation. Several studies have examined the impact of additional factors, such as ventilation, on the indoor hygrothermal environment [23,24,25]. Comparatively few studies have focused on the hygrothermal performance of different construction designs. Notably, some studies [8,26] have evaluated the hygrothermal conditions of diverse structures, ranging from above-ground warehouses to underground facilities.

In a previous paper [15], the authors showed that bioclimatic strategies can be effectively adopted for winery buildings that require specific interior hygrothermal conditions for wine aging and production. In particular, bioclimatic design techniques identified through psychrometric charts can ensure that interior conditions are optimized for wine aging while providing a comfortable environment for workers. Based on these premises, the goal of this work was to assess the thermal performance of significant possible configurations of winery buildings, defined as design models based on the literature, with different story dispositions with respect to ground level and construction solutions for the building envelope. The evaluations were performed in terms of energy consumption and compliance with the requirements for maintaining temperatures within optimal ranges. The novelty of this study, thus, lies in the numerical modeling approach adopted, which led to the identification of optimal constructive solutions aimed at energy efficiency and the control of the environmental conditions required for farm wineries of a given study area. The study was conducted through a dynamic thermal simulation, with reference to the climatic conditions of the Guadalupe Valley.

2. Materials and Methods

The methodology adopted in this research consisted in the following sequence of phases:

• Characterization of the area and the case study;
• Theoretical determination of optimal ranges of the thermal environment for wine;
• Design of a base model of a cellar for the requirements of use and thermal environment for production, aging, and tasting of wine;
• Dynamic simulation of six building models with bioclimatic design strategies;
• Dynamic simulation of the microclimate of the study area validated with monitoring data;
• Analysis of the results obtained with comparisons in percentage differences.

2.1. Study Area

The Guadalupe Valley is situated between the 30° and 50° northern latitudes, within the so-called geographic wine belts, regions recognized for their climates being conducive to vine cultivation. This enables the study area to compete with leading wine-producing countries worldwide, such as France, Spain, and Italy, the latter being the largest in terms of average annual production (Figure 2) [15,27].

The study area is located over 2000 km from Mexico City and approximately 100 km from the southwestern border of the United States, which facilitates the influx of international tourism. The valley has a territorial extension of 663.53 km², divided into three rural delegations: Francisco Zarco, San Antonio de las Minas, and El Porvenir. Around 120 farm wineries have been recorded in the region, ranging in size from small micro wineries to large commercial wineries [28]. Specifically, 77% of wine-makers adopt traditional production processes, obtaining overall less than 90 m³ of wine per year; the remaining wineries are medium-sized or industries, producing over 450 m³ per year. The research carried out focused on artisanal winery buildings, that is, on small producers.

Based on surveys carried out in the study area, 25% of the wine cellars were characterized: architectural and construction characteristics, data on equipment and machinery within the building, interior thermal mass, usage patterns, and single-point measurements of dry bulb temperature and relative humidity were collected. This allowed us to determine that the interior areas with the greatest requirement for ambient temperature and relative humidity control are those of wine production and aging. The most commonly used construction systems are reinforced concrete and metal structures, with a rectangular base and height construction typologies being the most adopted in the area.

2.2. Typological Model of Wine Cellars

A basic reference model of a wine cellar was designed based on the review of the scientific literature [29,30,31]. To define the design of the model, the relationship between the following factors was analyzed: (1) stages of wine production, (2) building design, (3) annual quantity of wine produced, and (4) dimensions (height, area, and volume).

The maximum dimensions obtained were a height of 4.50 m, a total area of 1473 m², and a volume of 6627 m³. The spatial units and their distribution were defined from a matrix of relations, and the plan form was defined with the aim of approaching a square configuration (Figure 3).

In order to define the level of priority for each element of the envelope (roofs, walls, floors) requiring the application of a bioclimatic strategy, test simulations were carried out in the DesignBuilder V4 program with the base model in three construction configurations: (1) natural ground level (above ground, B1), (2) semi-buried, and (3) underground (Figure 4). It is important to note that a sensitivity analysis was conducted for the two areas with the highest environmental control requirements, as well as the largest floor surfaces: production and aging.

The results obtained indicated that the roofs in all three building configurations contributed the most significant thermal load to the structure, particularly during the warmer months, from May to September. This period coincides with the peak usage of the wine production and aging areas, as it aligns with the harvest and grape collection season. Additionally, it was observed that while the walls were more insulated (as seen in the semi-buried building model), the roofs experienced higher heat gains (Figure 4).

A bioclimatic diagnosis was conducted to guide the decision-making process and assess the applicability of bioclimatic strategies. This diagnosis considered the climate of the study area, as well as the temperature and relative humidity requirements for a wine cellar, particularly for the winemaking and aging processes [15]. Therefore, bioclimatic strategies involving thermal mass (green roof, earth slopes on walls, and underground walls), shading (double roof and shaded walls), and thermal insulation (polyurethane, the most commonly used thermal insulator in the region) were applied to each building design model.

Bioclimatic design strategies were integrated into the base model obtained, resulting in the simulation of 11 buildings—6 wine cellar models for the aging area (SUt3) and 5 for the production area (SUt2)—which are mentioned in the following sub-sections.

The configurations resulting from the bioclimatic strategies implemented in the buildings are outlined in Figure 5 and include the following:

• Semi-buried (earth slopes on walls);
• Underground (aging area);
• Underground with a green roof for the aging area;
• Underground with a double roof and shaded walls for the aging area;
• Underground with 0.10 m of polyurethane on the roof of the aging area;
• Base model without strategies, used as a critical comparison case.

These six models were analyzed for the wine aging area. For the production area analysis, the following configurations were considered:

7.

Semi-buried;

8.

Semi-buried with a green roof for the production area;

9.

Semi-buried with 0.10 m of polyurethane on the roof of the production area;

10.

Underground with shaded walls due to the effect of a double roof in the aging area;

11.

Base model without strategies.

2.3. Thermal Simulation

The thermal simulations were carried out with DesignBuilder software, an EnergyPlus^® platform. In particular, the building was divided into 12 spatial units according to the requirements for the transformation of grapes into wine (SUt) and its commercialization (SUc); see Figure 3. The meteorological file (.epw, i.e., EnergyPlus weather file) used in this study was obtained from a year-long monitoring of weather conditions in the El Porvenir area, conducted due to the lack of official climatological data for the Guadalupe Valley. Data collection was performed using a micro weather station to measure dry bulb temperature, relative humidity, dew point, wind speed, wind direction, wind frequency, atmospheric pressure, precipitation, solar radiation, and UV (ultraviolet) radiation. Additionally, a latitude of 32.09°, a longitude of 116.61°, an elevation of 327 m above sea level, and wind exposure were factored into the models.

The climatic conditions of the site (Figure 6) under which the simulations were conducted indicated that the dry bulb temperature exceeded 30 °C during the months of July and September, with minimum temperatures ranging from 3.4 °C to 4.6 °C between December and February. Additionally, it was observed that the maximum radiation levels were registered between May and August, exceeding 1000 Wm⁻². Regarding relative humidity, the highest values were observed during the summer, from May to September, a period that coincides with the grape harvest season. These months are considered critical in terms of energy demand due to high temperatures and the increased occupancy resulting from the influx of tourists and temporary workers.

The air conditioning was considered as deactivated in the test simulations to obtain the effect of the building envelope materials on the dry bulb temperature and interior relative humidity. This was performed to define the element of the envelope in the models that was the weakest by providing the greatest thermal load (Figure 4). Occupancy schedules by users, refrigeration, heating, and lighting were used for the analysis of internal loads based on observations of the operating activities of the reference wine cellars. Furthermore, the exterior shadows were taken into account, while the thermal conductivity of the soil type for the Guadalupe Valley was considered as clayey silt (1.5 W m⁻¹ K⁻¹) [32,33]; this value was applied to the ground in contact with the buildings, including the earth slopes.

Preliminary simulations were carried out in TRNSYS only to define the depth of the underground building models by computing soil temperature up to a depth of 3 m at depth intervals of 0.25 m based on the weather temperature data. The results showed that the temperature stabilized below 3 m; thus, a depth of 4.5 m was defined for the floor of the underground level, ensuring its height was equal to that of the aboveground level.

For the DesignBuilder model, interior walls, stairwells, and the relationship between spaces were considered, as well as the transfer of energy between them; therefore, convective coefficients for walls, roofs, and floors were considered for the U-value calculation (

Table 1. Data summary for the building modeling.

Building Geometry	Area (m2)	Height (m)	Volume (m3)
Above-ground-level building (B1)	1471.30	4.5	6620.85
Semi-buried building (B2)	1471.30	4.5	6620.85
Underground building (B3)	1695.30	4.5	7628.85
Construction U-values (W/m2·K)	B1	B2	B3
External walls	2.32	2.32	2.562
Internal partitions	1.606	1.606	1.606
Roofs	3.639	3.639	3.646
Roofs with 0.10 m polyurethane	N/A	0.373	0.373
Green roof	N/A	0.963	0.963
Ground floor	3.633	3.633	3.633
Windows	5.89	5.89	5.89
Doors	2.079	2.079	2.079
Wine barrels	0.838	0.838	0.838
Internal loads	Equipment (W/m2)	Occupancy (People/m2)	Lighting (W/m2-100 lux)
Aging area	5	0.01	2
Production area	5	0.05	4
Heating, ventilation, and air conditioning (HVAC)	Aging area	Production area
Type of HVAC system	Packaged Direct Expansion (PDX)	Packaged Direct Expansion (PDX)
Coefficient of performance (COP)	4	4
Heating	On	On
Winter clothing	1 clo	1 clo
Cooling	On	On
Summer clothing	0.5 clo	0.5 clo
Cooling setpoint	15 °C	25 °C
RH setpoint for humidification	30%	30%
RH setpoint for dehumidification	75%	75%
Simulation calculation options
Solution algorithm	Conduction transfer function (CTF)
Surface convection algorithm—inside		TARP
Surface convection algorithm—outside		DOE-2
Time steps per hour		2

). The proposed models took into account the structural design of slabs and walls, as well as their energy exchange with the interior environment; the simulated buildings included steel beams in their structure for spans greater than 10 m; for the wine aging area, six beams were placed at a spacing of 3.7 m, and these elements were modeled as subsurfaces in Design Builder with independent heat transfer values to ensure accuracy in the thermal calculation (Table 1).

In the production area, the following values were considered: clothing insulation (clo; it is considered as a parameter affecting the assessment of thermal comfort for occupants [34]), space illumination (lux), fresh air requirement (ls⁻¹ per person), mechanical ventilation per area (ls⁻¹ m⁻²). For the aging area, the activity values were considered as those of a low-occupancy industrial space, given that wine barrels are the primary element in this area and contribute significantly to the interior thermal mass. Consequently, the number of barrels per m² was taken into account. A U-value of 0.838 W/m²·K per barrel was applied, with a maximum storage capacity of 90 m³ of wine. The parameters for the simulation of the green roof were defined based on the literature [35,36]. Theoretical range averages were established based on various authors: optimal for aging (10 °C to 15 °C) and wine production (15 °C to 25 °C); see

Table 2. Optimal indoor temperature for the aging area in a wine cellar according to the scientific literature.

Author (s)	Dry Bulb Temperature (°C)
Troost [37]	9–15
Boulton et al. [38]	5–15
Hidalgo Togores [39]	9–12
Mazarrón and Cañas [40]	≤18
Steiner [41]	13–20
Bondiac [42]	10–12
Marescalchi [43]	15–20
Marrara et al. [44]	12–16
Considine and Frankish [45]	≤20
	<16
Vogt [46]	12
	8–12

.

The validation of the thermal simulation was carried out with an empirical method, which was derived from the scientific literature [47] and applied to this research. The method consisted of a comparative statistical analysis of data from the simulation environment with data obtained by monitoring. A reference cellar was used, which was located in Ejido El Porvenir in the Guadalupe Valley. The dry bulb temperatures of the warm period from May to September and the cold period from December to February were compared. These data were obtained through a thermal simulation with the DesignBuilder software and from on-site monitoring.

A total of 3672 dry bulb temperature data of the warm period, which had been collected in the period of May–September, were analyzed. The comparison of the monitoring results with the simulation carried out had a maximum positive error of +4.4 °C, a maximum negative error of −3.6 °C, and a graphical error opening of ±4 °C (Figure 7). It is necessary to mention that when the simulation data were lower than the monitoring data, the error was considered positive, and when the simulation presented data greater than the monitoring data, the error was considered negative.

A total of 2157 data of the cold period were analyzed; a maximum positive error of +1.8 °C and a maximum negative error of −1.7 °C were obtained, and the graphical opening of the error was ±1.75 °C, as shown in Figure 8.

In the warm period, the mean absolute deviation was 1.58 °C and the mean absolute error percentage was 8.7% between the simulation and the thermal monitoring, while the coefficient of multiple determination (R2) was 0.04, which showed a direct relationship between the two groups of data compared. In the cold period, the mean absolute deviation was 0.56 °C, the mean absolute error percentage was 3.47%, and the R2 was 0.16 (

Table 3. Validation metrics of the results obtained through the thermal simulation model.

Parameter	Warm Period	Cold Period
Mean error (°C)	0.54	0.26
Mean absolute deviation (°C)	1.58	0.56
Multiple determination coefficient (R2)	0.04	0.16
Mean absolute percentage error (%)	8.67	3.47
Mean error in daily maxima (°C)	0.50	0.10
Mean absolute deviation in daily maxima (°C)	1.29	0.48
Multiple determination coefficient in daily maxima (R2)	0.002	0.27
Mean absolute percentage error in daily maxima (%)	6.95	2.91

).

The mean error (°C) obtained in this study for both the warm and cold periods was within the acceptable ranges for the empirical validation of building simulations with EnergyPlus, according to Mateus et al. [47] whose study had a reference range for acceptable errors: they mentioned errors of 4.3 °C to 7 °C. Thus, the metrics of the results of the new simulations carried out were considered satisfactory. A comparison was also made with the values obtained for the mean absolute error percentage (%), and the simulation of the proposed models fell into the classification of excellent (3.47%) in the cold period and very good in the warm period (8.67%) according to the classification of Ali and Abustan [48].

3. Results and Discussion

3.1. Cold Period

A “cold period” was defined as including the months of December, January, and February, for which the following parameters were analyzed:

• Indoor dry bulb temperature (°C);
• Monthly degree-hours (°C h) outside and inside the optimal hygrothermal range for wine;
• Sensible cooling or heating required (kWh).

The data obtained from the indoor dry bulb temperature showed that, on average, for 61% of the hours, the DBT was above the limit of 15 °C, and for 39% of the hours of this period, it was within the optimal range established for wine aging (10 °C to 15 °C). This allowed us to determine that for this area of the cellar, during the cold period, the use of heating is not necessary, but electromechanical cooling is required in all the proposed buildings to reach the temperature values of the defined optimal range.

Regarding the analysis of the indoor temperature oscillation, in the model with a double roof, the aging area cover was shaded, but it was in contact with the outside air. This was reflected in a difference of 5.25 °C between the maximum and minimum DBTs recorded, compared to the building with a green roof with an oscillation of 3.61 °C. The building with a green roof presented indoor temperature values above the optimal range, but it was one of the most stable models, having a smaller difference between the minimum and maximum hourly DBTs (

Table 4. Descriptive statistics of the indoor temperatures computed in the winery model for the aging room in the cold period.

Building Model	Maximum Interior DBT * (°C)	Minimum Interior DBT (°C)	Average Interior DBT (°C)	Temperature Oscillation ** (°C)	Hours Outside Optimal Range (%)
Base building	19.31	13.24	15.62	6.07	62.77
Semi-buried	19.12	13.42	15.70	5.70	69.09
Underground	18.46	13.35	15.44	5.11	53.16
Underground building with green roof	18.01	14.40	16.11	3.61	87.73
Underground with double roof	18.23	12.98	15.13	5.25	21.64
Underground with 0.10 m polyurethane	18.21	14.05	15.82	2.39	69.72

* DBT = Dry bulb temperature, ** Temperature oscillation between the maximum and minimum.

). This result is in line with the findings published in [15], which underline that thermal mass encompasses design strategies with significant environmental and architectural benefits for commercial winery buildings, including green roofs and vegetated walls. In fact, these solutions contribute to regulating indoor temperature variations and delaying peak temperature occurrences. Consequently, they enhance thermal comfort and mitigate heat gain from external sources.

The hourly data obtained from the indoor dry bulb temperature allowed for a monthly analysis of the degree-hours of the aging area. The temperature range of 10 °C to 15 °C established for the said area, derived as an average of the ranges reported in Table 2, was considered in the calculation. The conditional formula used was the following [20]:

If X > 15 then dh = X − 15

(1)

If 10 ≤ X ≤ 15 then dh = 0

(2)

where dh is the degree-hours, and X is the hourly indoor dry bulb temperature obtained with the thermal simulation.

The minimum number of degree-hours required was found in the building with the double-roof strategy, followed by the model with polyurethane; the building with underground walls turned out to be the best configuration, followed by the model with semi-buried walls (Figure 7).

The month with the highest number of degree-hours above the range was December, and the month with the minimum degree-hours was February. The above result shows that during this period, buildings tend to store heat, in addition to the thermal load contributed by the wine processes inside the barrels and operational activities in the area.

The sensible cooling requirement analysis by zone (kWh) showed that the models with the lowest cooling requirement were the building with a double roof, the building with underground walls, and the building with thermal insulation with polyurethane (Figure 8). In these results, the energy values are negative because they represent the amount of energy that needs to be removed from the building.

Although the double-roof strategy produced a lower amount of energy per month compared to the green roof, the latter had less oscillation in the interior temperature, which meant greater stability in the environmental conditions for the wine. In February, i.e., the month with the lowest sensible cooling requirement, the building with the polyurethane roof required a lower amount of energy to keep the aging area within the recommended interior temperature range, compared to the other buildings. When comparing the period totals, for the simulated buildings, it was found that the highest cooling requirement was for the underground building with a green roof (9956 kWh), which indicated that the thermal mass in contact with the roof allowed heat to be stored and delayed energy loss from the building. The lowest amount of sensible cooling required was found in the underground building with a double roof (4503 kWh); this was because the second roof provided shading to the building during hours of the greatest solar radiation and allowed for contact with the outside air. This strategy decreased the energy gain per roof by 45% less compared to the base building, which was considered the critical case without the applied strategies (Figure 8).

3.2. Warm Period

A “warm period” was defined as including the months of May to September, and for this period, the following parameters were analyzed:

• Indoor dry bulb temperature (°C);
• Monthly degree-hours (°C h);
• Sensible cooling or heating (kWh).

For over 99% of the hours of the warm period (3665.5 h on average among the six cases), the DBT was outside the established optimal range of 10 °C to 15 °C; the rest of the hours were within the range. This allowed us to determine that for this area, the use of electromechanical cooling systems is necessary for most of the hours of the period.

The results obtained for indoor dry bulb temperature (DBT) showed that in the base building, the maximum indoor DBT was 24.87 °C, in the semi-buried building 24.57 °C, in the underground building 23.23 °C, in the underground building with a green roof 21.23 °C, in the model with a double roof 21.43 °C, and in the building with polyurethane on the roof 20.59 °C.

The best performance in terms of indoor DBT was obtained with the model with polyurethane thermal insulation, a difference of 17% less compared to the base building considered as a critical case and 3% less compared to the model with a green roof (

Table 5. Descriptive statistics of the indoor temperatures computed in the winery model for the aging room in the warm period.

Building Model	Maximum Interior DBT * (°C)	Minimum Interior DBT (°C)	Average Interior DBT (°C)	Temperature Oscillation ** (°C)	Hours Outside Optimal Range (%)
Base building	24.87	15.10	20.83	9.77	100.00
Semi-buried	24.57	15.14	20.69	9.43	100.00
Underground	23.23	14.83	19.86	8.40	99.75
Underground building with green roof	21.23	15.08	18.82	6.15	100.00
Underground with double roof	21.43	14.00	18.48	7.43	99.42
Underground with 0.10 m polyurethane	20.59	14.59	18.23	5.99	99.75

* DBT = Dry bulb temperature, ** Temperature oscillation between the maximum and minimum.

).

In the degree-hour analysis for the aging area, it was found that the critical months of the warm period were July, August, and September. The models with the lowest number of monthly degree-hours were the building with polyurethane, the building with a double roof, and the building with a green roof (Figure 9).

In the month of August (when the maximum values were recorded), the base building had 5443 degree-hours above 15 °C, which was the maximum limit of the optimal range; in the building with polyurethane, 3333 degree-hours were estimated, 38% less; and in the building with a green roof, during the same month, 3823 degree-hours were observed, a difference of 30% compared to the base building and 13% compared to the building with polyurethane (Figure 9).

Sensible cooling was analyzed on the basis of kWh, as in the degree-hour analysis. August was the critical month of the period, the one that required the greatest amount of energy for cooling the aging area (Figure 10). These results confirm that underground cellars exhibit greater thermal stability during the summer months, offering improved indoor conditions and minimizing energy loss compared to above-ground wineries [18]. In general, the scientific literature shows that high-thermal-mass structures are particularly effective in hot climates [49].

The monthly cooling requirement in August was more than 28,207 kWh for the base building, while for the building with polyurethane, the total cooling for the same month was 5815 kWh, a difference of 80%. The model that performed well was the building with a green roof, with a difference of 78% less energy compared to the base building and 6.5% compared to the model with polyurethane thermal insulation. These results indicate that green roofs are an appropriate bioclimatic strategy to meet the indoor temperature and humidity requirements of the aging area in winery buildings.

It is important to mention that cooling was required every month of the year, mainly in the months of June to October, even in the months of the cold period. This may be due to the temperature range used for the simulations of the aging area, which was 10 °C to 15 °C (Table 2).

4. Conclusions

The bioclimatic strategies of thermal mass, shading, and electromechanical cooling applied in the design of artisanal winery buildings in the Guadalupe Valley optimize the hygrothermal performance of the buildings by generating an interior environment within the ranges of dry bulb temperature and relative humidity suitable for wine aging. A correct bioclimatic design of these types of buildings that require strict control of interior temperature and humidity can be a sustainable alternative to minimize energy consumption for air conditioning, both in new constructions as well as in restorations or remodeling.

The constructive location of the wine aging area turned out to be a determining factor in the oscillation of the interior ambient temperature; this thermal effect coincides with what happens in traditional Spanish underground wine cellars that are still used. The underground model combined with a green roof allowed the interior temperature to be reduced in the months of the warm period; its performance was similar to that obtained with 0.10 m of polyurethane insulation, considered the most widely used system in the region and which had fewer environmental advantages than a green roof.

In the cold period, the model with the best thermal performance was the green roof due to the heat storage effect of the thermal mass in direct contact with the roof. Values above the optimal range were obtained; however, its temperature differential between the maximum and minimum values was 3.61 °C, the lowest compared to the other models. In the warm period, it also had the lowest DBT differential (6.15 °C). In both cases, the values were very close to those obtained with the polyurethane model, with less than a 35% difference.

The bioclimatic strategy recommended to ensure optimal hygrothermal performance in the aging of wine is the green roof. In addition to the fact that the soil used is recovered by restoring the soil occupied by the building with green areas, it can be attractive for tourism and serve as an urban garden, or if its design allows, it can include the planting of vine varieties.

The double-roof building also proved to be a bioclimatic strategy that reduced the interior dry bulb temperature. Its construction cost can be lower compared to a green roof’s and equally attractive when its design is considered, in addition to the fact that it can be an element of adaptation for existing buildings.

The study led to the conclusion that the interior thermal environment of a building located in the Guadalupe Valley without any strategy applied, whether passive or active, will be above the optimal range for wine aging (10 °C to 15 °C) 100% of the time for the warm period and more than 60% of the time for the cold period, which will require the mandatory use of electromechanical cooling systems to ensure product quality and avoid wine losses due to evaporation. Not considering the bioclimatic design of winery buildings can result in a future threat to the quality of wine produced in the area due to the poor preparation of buildings to counteract temperature increases due to climate change.